Pneumocystis pneumonia is a fungal lung infection caused by Pneumocystis jirovecii in people with weak immune systems, especially HIV with a CD4 count below 200 and patients on steroids or chemotherapy. It causes low oxygen that is often worse than the lung exam suggests.
Key symptoms
- Shortness of breath that worsens over days to weeks
- Dry cough
- Fever and fatigue
- Breathlessness when walking or climbing stairs
- Weight loss or thrush in people with HIV
What you find on exam
- Fast breathing and fast heart rate
- Low oxygen saturation that drops with exertion
- Lungs often clear or with mild crackles
- Oral thrush or other signs of a weak immune system
Tests
- Chest X-ray: diffuse haziness in both lungs, may be normal early; CT if unclear
- Arterial blood gas; LDH is often high
- Induced sputum or bronchoscopy with PCR or staining
- HIV test and CD4 count; beta-D-glucan supports the diagnosis
Treatment basics
- Trimethoprim-sulfamethoxazole (TMP-SMX) for 21 days
- Add prednisone if PaO2 is below 70 mmHg or the A-a gradient is 35 or more
- Alternatives for sulfa allergy: primaquine with clindamycin, or IV pentamidine
- Start HIV treatment within 2 weeks
- TMP-SMX prophylaxis afterward until immune function recovers
Red flags
- Oxygen saturation below 90% or rising oxygen needs
- Sudden chest pain and worse breathing (pneumothorax)
- Confusion, exhaustion or low blood pressure
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Sources: NCCPA PANCE Content Blueprint; NBOME COMLEX-USA clinical presentations; AAMC Core Entrustable Professional Activities (Core EPAs). Written by Making Synapses. Making Synapses is not affiliated with these organizations.